Bromocriptine and prostatic carcinoma: plasma kinetics, production and tissue uptake of 3H-testosterone in vivo

The influence of the anti-prolactin bromocriptine on plasma kinetics, production rate and tissue uptake of testosterone was investigated in 15 patients with newly diagnosed stages C and D prostatic carcinoma. Bromocriptine was given for 5 days in a daily dose of 15 mg. orally. The studies were performed with the single injection technique using the 2-compartment model. Plasma testosterone, serum prolactin, and luteinizing and follicle-stimulating hormones were determined initially. Blood samples were drawn up to 5 hours after the injection of 3H-testosterone. For tissue studies a transrectal needle biopsy was done 3 hours post-injection. Bromocriptine suppressed prolactin and the endogenous testosterone level. Furthermore, it favored the elimination of 3H-testosterone, lowered the production rate of testosterone and hampered the in vivo uptake of the 3H-label into prostatic carcinoma tissue. Finally, the grading of the tumor lesions affected only the pre-bromocriptine uptake of radioactive androgens and not the uptake in response to bromocriptine. The potential clinical impliications of these observations are discussed.